Method for separating a 2- and 4-chlorobiphenyl from the corresponding hydroxybiphenyl compounds

ABSTRACT

2-Chlorobiphenyl, 4-chlorobiphenyl or mixtures thereof may be separated from a mixture with the corresponding hydroxybiphenyl compound by adding to the mixture of such compounds an azeotropic agent which is a glycol, glycol monoalkyl or phenyl ether, glycerol, glycerol alkyl ether, alkanolamine or dialkylenetriamine having a boiling point within about 45* C. of the halobiphenyl compound at atmospheric pressure, and then fractionally distilling the mixture thus formed at a pressure of up to about 200 mm. Hg. absolute.

United States Patent Seeburger et al.

[54] METHOD FOR SEPARATING A 2- AND 4-CHLOROBIPHENYL FROM THE CORRESPONDING HYDROXYBIPHENYL COMPOUNDS [72] Inventors: Harold O. Seeburger; Lee H. Horsley, both of Midland, Mich.

[73] Assignee: The Dow Chemical Company, Midland,

Mich.

[22] Filed: Oct. 15,1969 [21] Appl.No.: 866,734

[51] Int. Cl. ..B01d 3/36, C07c 25/ 18 [58] Field ofSearch ..203/48,50, 55,56,57,59, 203/63, 64, 65, 66, 70; 260/707, 649, 649 DP, 620

[56] References Cited UNITED STATES PATENTS 2,776,937 1/1957 Filar ..203/48 3,655,523 [451 Apr. 11,1972

Britton ..203/48 1,836,307 12/1931 Britton 1,890,427 12/1932 Britton et al.... ..203/48 1,951,577 3/1934 Malowan ..260/649 DP 2,442,229 5/1948 Berg et al ..203/59 X OTHER PUBLICATIONS Chemical Abstract Vol. 48 1954) Azeotropy Distill.

Primary Examiner-Wilbur L. Bascomb, Jr. Attorney-Griswold and Burdick [57] ABSTRACT 6 Claims, No Drawings BACKGROUND OF- TI-IE INVENTION Chlorinated biphenylcompounds may be hydrolyzed to form the corresponding hydroxybiphenyl J compound I where the. hydroxyligroupzreplaces. the halogen. The-hydrolysis is 'rarelyjfievercomplete; resultingin a reaction productthat is-a mixture of rthe halogenatedn'biphenyl and the corresponding hydroxybiphenyl. Theschloro and hydroxy compounds have close boiling .points -andare extremely difficult to separate. by

ordinary-distillation: This difficulty-has initiated a-search for a' convenient and effective method of separating the .halogenatedtbiphenylfromthe corresponding hydroxy compound.

SUMMARY OF THE INVENTION According to-the-present invention, 2-chloro-biphenyl, 4- clilorobiphenyl .or mixturesthereof are separated-from the corresponding hydroxylcompounds by-adding to the mixture of such compounds an azeotropic agent which-isa glycol,

glycol monoalkylorphenylether, glycerol, glycerol'alkyl. ether, alkanolamine or dialkylenetriamine having a. boiling point withinabout 45 C. ofthe chlorinated component at atmospheric pressure, and then fractionally distilling the mixture thus formed at apressureaot' up to 200 mm. Hg. absolute. The process of the present invention is. conveniently adapted to either a batch or. preferably a continuous flow operation. In a.continuous flow operation, a mixture ofthe, chlorobiphenyl, the corresponding hydroxybiphenyLtand the azeotropic agent are fed into an intermediate point of a distillation column. The column is .heldjunder apressure less than 200mm. Hg. absolute and is heated to distill the lower boilingfraction. The halohydrocarbon andthe azeotropic agent are collected as the distillate, and the corresponding hydroxy compound is collectedas the residue.

The essential and novelfeature of the present inventionis theseparation of" mixtures of 2-chlorobiphenyl, 4- chlorobiphenyl or mixtures thereof from the corresponding hydroxybiphenyl compounds o-phenylphenol and p-phenylphenol bythe use of-these particular azeotropic agents. The azeotropic agents may bea lower .alkylene glycol, lower alkylene glycol monoalkyl or phenylether, glycerol, glycerol alkyl' ether, alkanolamine'or lo'wer dialkylenetriamine having a boiling-point within 45C. of the halogenatedhydrocarbon at atmospheric pressure. Azeotropic agents having a boiling point-within 30 C; of the'halogenated hydrocarbon, and those having a boiling point below the halobiphenyl compound are preferred. Representative examples of these agents include: lower alkylene glyeols'such as diethylene glycol, triethylene glycol, dipropyleneglycol,.tripropylene glycol and dibutylene glycol; glycol monoalkyl others such as triethylene glycol monomethyl ether, ethylene glycol phenyl ether, diethylene glycol-.n-butyl ether tripropylene glycol monomethyl ether and propylene glycolmonophenyl ether; glycerol alkyl ethers such as glycerol monomethyl ether; alkanolamines such as diethanolamine, triethanolamine, dipropanolamineand diisopropanolamine; and lower dialkylenetriamines such as diethylenetriamineanddipropylenetriamine. Of these compounds, triethylene glycol monomethyl ether, diisopropanolamine, dipropylenetriamine and diethylene glycol are specially preferred azeotropic agents.

The azeotropicdistillation of the invention may suitably be applied to 2-chlorobiphenyl, 4-chlorobiphenyl or mixtures thereof. Such compounds are well known and readily available. A mixture of all four components may be separated by .azeotropic distillation by adding an azeotropic agent to the 3 mixture and distilling both chlorinated compounds simultanelolously. In the preferredpractice of the present invention, 2-

L chlorobiphenyl is separated from o-phenylphenol.

The comparative concentrations of the halogenated comlpound and the corresponding hydroxy] compound may vary widely. Essentially any concentration of the two'or more components in the'mixturemaybe separated by the present invention. In the preferred practice of the invention, a minor 1 amount of the halohydrocarbon is present in the mixture.

; The amountofazeotropic agent-added to the mixture of the chlorobiphenyl and the corresponding hydroxy compound may. vary widely aswillbe seen-in the Examples. Generally, the smallest amount of azeotropic agent required to give the desired separation is used so that the heat introduced during distillation is most efficiently employed. The amount of azeotropic agent requiredis dependent on the amount of halohydrocarbon in the mixture, the azeotropic agent employed, the operating pressure, andthe apparatus used in the distillation. The optimum amount of azeotropic agent for a particular system is best determined by experience using these factors as a guide.

Many of the azeotropic agents of the present invention are at least partially insoluble in the halohydrocarbon. Accordingly, the condensed distillate usually forms two phases. This phenomenon is especially advantageous since it permits easy separation of the azeotropic agent from the halohydrocarbon and simple recycling of the azeotropic agent to the distillation.

After the addition of the azeotropic agent, the distillation of themixture is-conducted under a subatmospheric pressure of up to about 200 mm. Hg. absolute, with pressures of l to 100 1 mm- Hg. absolute being preferred. As the pressure is increased, the distinctness of the separation is decreased and more of the hydroxy compound appears in the distillate.

Thus, by using the azeotropic agents of the present invention, 2-chlorobiphenyl may be separated from orthophenylphenol, 4-chlorobiphenyl may be separated from p-phen- I ylphenol or mixtures of the four components may be separated in a convenient and economical process.

I SPECIFIC EMBODIMENTS ylphenol To a mixture containing 95 percent by weight o-phenylphenol (b.p. 275 C.) and approximately 5 percent by weight 2-chlorobiphenyl (b.p. 268 C.), 25 percent by weight of an azeotropic agent was added and 3 to 15 percent of the mixture was distilled at reduced pressure in a 1% inch x 30 inch column packed with V4 inch Berl saddles at a 5/1 reflux ratio. The azeotropic agents, distillation conditions and results rqshsnvei able TABLE I [Separation of 2-chlorobiphenyl (Z-CBP) from o-phenylphenol] Alzeotrople agent Diprop enetrinmiue. Dleigy one glyeoL. 0

Do Dlothunolmnino Gl carol Tr propylene glycol Triethylcne glycol B.p., O. at Pressure, 760 mm. Hg mm.

Wt. percent Z-CBP (azeo. Dist'n. Wt. percent agent tree) temp, azeo. agent C. in dist.

Hg Original Distillate Residue 10 119 75 5. 23 9S. 5 D. 2 249 10 127 50 5. 40 100. 0 0. 9 240 10 122 75 6. 98, 0 0. 1 245 10 125 6!) 4. 40 82. 5 0. 1 245 100 175 58 5. 75 94. 4 0. 8 245 200 197 51! 6. 80 73. 5 2. 6 268 10 139 3. 5 6. 10 67. 6 0. 7 290 10 136 3. 8 0. 70 64. 0 0. 4 267 10 140 2. 2 5. 20 59. 0 1. 6 289 10 I37 0.8 6. 4 58. 0 1.2

Example 1 Separation of 2-Chlorobiphenyl from o-Phen- Example 2 Separation of 2- and 4-Chlorobiphenyl from oand p-Phenylphenol To a mixture containing 67.5 wt. percent o-phenyl-phenol (b.p. 275), 22.5 wt. percent p-phenylphenol (b.p. 305), 5 wt. percent 2-chlorobiphenyl (b.p. 268), and 5 wt. percent 4- chlorobiphenyl (b.p. 282) was added 25 wt. percent diethylene glycol as an azeotropic agent. The mixture was distilled in the same manner as shown in Example 1. The distillate contained 49 wt. percent of the azeotropic agent, the aromatics in the distillate were 99.3 wt. percent chlorinated biphenyls and the residue contained only 0.75 wt. percent chlorinated biphenyl.

In the same manner as described in the examples above, 4- chlorobiphenyl may be separated from a mixture with p-phenylphenol by using any of the azeotropic agents of Example 1.

We claim:

1. A method for separating 2-chlorobiphenyl, 4- chlorobiphenyl or mixtures thereof from a mixture with o- 'phenylphenol, p-phenylphenol or mixture thereof, comprising adding to the mixture of the chlorinated biphenyl and the corresponding hydroxybiphenyl compound an azeotropic agent 3. The method of claim 1 wherein the azeotropic agent boils I at a temperature below the chlorobiphenyl compound at atmospheric pressure.

4. The process of claim 1 wherein the azeotropic agent is triethylene glycol monomethyl ether, diisopropanolamine, dipropylenetriamine or diethylene glycol.

5. The process of claim 1 wherein 2-chloro-biphenyl is separated from o-phenylphenol.

6. The method of claim 1 wherein the fractional distillation is conducted at a pressure of l to mm. Hg. absolute. 

2. The method of claim 1 wherein the azeotropic agent has a boiling point within 30* C. of the chlorobiphenyl compound at atmospheric pressure.
 3. The method of claim 1 wherein the azeotropic agent boils at a temperature below the chlorobiphenyl compound at atmospheric pressure.
 4. The process of claim 1 wherein the azeotropic agent is triethylene glycol monomethyl ether, diisopropanolamine, dipropylenetriamine or diethylene glycol.
 5. The process of claim 1 wherein 2-chloro-biphenyl is separated from o-phenylphenol.
 6. The method of claim 1 wherein the fractional distillation is conducted at a pressure of 1 to 100 mm. Hg. absolute. 